Alkali metal diarylphosphides are useful as raw materials for the production of cycloalkyldiarylphosphines such as neomenthyldiphenylphosphine and menthyldiphenyl-phosphine. Such phosphines are examples of ligands which impart to transition metal complexes the potential for diastereomeric interactions with unsaturated organic substrates, thus making asymmetric synthesis possible. Note in this connection, J. D. Morrison and W. F. Masler, J. Org. Chem., 1974, Vol. 39, No. 2, pages 270-272. Neomenthyldiphenylphosphine is of particular importance for the preparation of noble metal catalysts useful in the synthesis of certain pharmaceuticals such as naproxen, ketoprofen, ibuprofen, etc.
Heretofore, sodium diphenylphosphide has been produced by reacting triphenylphosphine with about 4 equivalents of sodium. The yield of such reaction has been less than about 57%. It is also known that 2 equivalents of alkali metal dissolved in liquid ammonia can reduce triphenylphosphine to alkali metal diphenylphosphide. Reactions with liquid ammonia require special conditions and equipment, and are not desirable for commercial operations.
Because of the shortcomings inherent in these previously-known processes, a need has existed for a commercially feasible process capable of producing alkali metal diarylphosphides of high purity in high yields. This invention is deemed to fulfill this need most expeditiously.